This is a very helpful workflow - it functions well and I also edited it to post a notification that says "Renamed from {var:oldfilename} to {var:newfilename}".
However I did notice that if you rename file A the name of an existing file B of the same type in the same directory it overwrites file B (and I have no idea where the old one goes - not in the trash . Hopefully and presumably something the filesystem can manage). Similarly renaming folder A to the name of folder B in the same directory will move folder A into folder B.
Ideally both of these scenarios would report an error and not follow through with the operation, or utilize similar behavior as Finder, by addending "1" "2" "3" etc. to the new file name (or if that's not possible perhaps addending "copy from {time}" to the filename using the {time} dynamic placeholder as a unique identifier)
Let me if I'm missing something, but for now I won't use this since I may accidentally delete files with it.
Thanks!